#include <iostream>

class Test
{
public:
    //初始化列表
    //const变量必须在初始化列表中初始化
    Test():a(0)
    {
    }
    void show()
    {
        std::cout << this->a << std::endl;
    }

private:
    const int a;
};

int main()
{
    Test t;
    t.show();

    return 0;
}